Aqueous solutions of alkali-metal salts of neutral .alpha.-amino acids are produced, e.g., in the alkaline hydrolysis of the corresponding .alpha.-amino nitriles.
The recovery of free, neutral .alpha.-amino acids from aqueous solutions of their alkali-metal salts by means of a strongly acidic cation exchanger in the H.sup.+ form is known (cf. e.g. Greenstein and Winitz, Chemistry of the Amino Acids, Wiley, New York and London, 1961, p. 1459 ff.). In this process, the alkali-metal cations and the .alpha.-amino acids are bound to the ion exchanger. After the ion exchanger has been washed out with water, the .alpha.-amino acid is eluted with a dilute, aqueous solution of ammonia. The ammonia is expelled when the eluate is evaporated, and it can, if necessary, be recovered. The free .alpha.-amino acid can be isolated from the residue. However, this known method has several disadvantages: Since the alkali-metal cations and the .alpha.-amino acid are bound to the ion exchanger, its effective capacity for the bonding of the alkali-metal cations is, at best, only half-available. Ammonia is required as an additional auxiliary agent. And, finally, the eluates are strongly diluted in comparison to the initial solutions and considerable amounts of water must therefore be evaporated, especially in the case of readily water-soluble .alpha.-amino acids such as glycine, alanine or .alpha.-amino butyric acid.